Gutless emperor trembled after very macho glance (8,4)

'glance' is the definition.
('butcher's hook' is Cockney rhyming slang for look)

'gutless emperor trembled after very macho' is the wordplay.
'gutless' means to remove the middle letters.
'trembled' becomes 'shook' (shake can mean to tremble).
'after' says to put letters next to each other.
'very macho' becomes 'butch' (butch can mean very masculine).
'emperor' with its centre taken out is 'er'.
'er'+'shook'='ershook'
'ershook' after 'butch' is 'BUTCHERS HOOK'.